<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>ownKeys</title>
</head>
<body>
    <script>
        let obj = {
            'foo': 0,
            [Symbol()]: 'hello'
        }

        console.log(obj);   // {foo: 0, Symbol(): "hello"}
        console.log( Object.getOwnPropertyNames(obj) ); // ["foo"]
        console.log( Object.getOwnPropertySymbols(obj) );   // [Symbol()]
        console.log( Reflect.ownKeys(obj) );    // ["foo", Symbol()]
    </script>
</body>
</html>